[FFmpeg-devel] [PATCH] lavf: add subfile protocol.
Lukasz Marek
lukasz.m.luki at gmail.com
Tue Feb 25 23:04:43 CET 2014
On 25.02.2014 21:55, Nicolas George wrote:
> Signed-off-by: Nicolas George <george at nsup.org>
> ---
> Changelog | 1 +
> doc/protocols.texi | 19 +++++++
> libavformat/Makefile | 1 +
> libavformat/allformats.c | 1 +
> libavformat/subfile.c | 145 +++++++++++++++++++++++++++++++++++++++++++++++
> libavformat/version.h | 2 +-
> 6 files changed, 168 insertions(+), 1 deletion(-)
> create mode 100644 libavformat/subfile.c
>
> diff --git a/Changelog b/Changelog
> index 2785b3a..e57fc46 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -28,6 +28,7 @@ version <next>
> - Support DNx444
> - libx265 encoder
> - dejudder filter
> +- subfile protocol
Why? :)
...did you remove 3 entries?
>
> version 2.1:
> diff --git a/doc/protocols.texi b/doc/protocols.texi
> index 2c84265..77772ae 100644
> --- a/doc/protocols.texi
> +++ b/doc/protocols.texi
> @@ -949,6 +949,25 @@ this binary block are used as master key, the following 14 bytes are
> used as master salt.
> @end table
>
> + at section subfile
> +
> +Virtually extract a segment of a file or another stream.
> +The underlying stream must be seekable.
> +
> +Accepted options:
> + at table @option
> + at item start
> +Start offset of the extracted segment, in bytes.
> + at item end
> +End offset of the extracted segment, in bytes.
> + at end table
> +
> +Example: extract a chapter from a DVD VOB file (start and end sectors
> +obtained externally and multiplied by 2048):
> + at example
> +subfile,,start,153391104,end,268142592,,:/media/dvd/VIDEO_TS/VTS_08_1.VOB
> + at end example
> +
> @section tcp
>
> Trasmission Control Protocol.
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index 9ef81cc..dd13fd0 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -464,6 +464,7 @@ OBJS-$(CONFIG_RTMPTS_PROTOCOL) += rtmpproto.o rtmppkt.o
> OBJS-$(CONFIG_RTP_PROTOCOL) += rtpproto.o
> OBJS-$(CONFIG_SCTP_PROTOCOL) += sctp.o
> OBJS-$(CONFIG_SRTP_PROTOCOL) += srtpproto.o srtp.o
> +OBJS-$(CONFIG_SUBFILE_PROTOCOL) += subfile.o
> OBJS-$(CONFIG_TCP_PROTOCOL) += tcp.o
> OBJS-$(CONFIG_TLS_PROTOCOL) += tls.o
> OBJS-$(CONFIG_UDP_PROTOCOL) += udp.o
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index 0e70b6e..16a3ae3 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -338,6 +338,7 @@ void av_register_all(void)
> REGISTER_PROTOCOL(RTP, rtp);
> REGISTER_PROTOCOL(SCTP, sctp);
> REGISTER_PROTOCOL(SRTP, srtp);
> + REGISTER_PROTOCOL(SUBFILE, subfile);
> REGISTER_PROTOCOL(TCP, tcp);
> REGISTER_PROTOCOL(TLS, tls);
> REGISTER_PROTOCOL(UDP, udp);
> diff --git a/libavformat/subfile.c b/libavformat/subfile.c
> new file mode 100644
> index 0000000..e683be5
> --- /dev/null
> +++ b/libavformat/subfile.c
> @@ -0,0 +1,145 @@
> +/*
> + * Copyright (c) 2014 Nicolas George
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public License
> + * as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "libavutil/avassert.h"
> +#include "libavutil/avstring.h"
> +#include "libavutil/opt.h"
> +#include "avformat.h"
> +#include "url.h"
> +
> +typedef struct SubfileContext {
> + const AVClass *class;
> + URLContext *h;
> + int64_t start;
> + int64_t end;
> + int64_t pos;
> +} SubfileContext;
> +
> +#define OFFSET(field) offsetof(SubfileContext, field)
> +#define D AV_OPT_FLAG_DECODING_PARAM
> +
> +static const AVOption subfile_options[] = {
> + { "start", "start offset", OFFSET(start), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
> + { "end", "end offset", OFFSET(end), AV_OPT_TYPE_INT64, {.i64 = 0}, 0, INT64_MAX, D },
> + { NULL }
> +};
> +
> +#undef OFFSET
> +#undef D
> +
> +static const AVClass subfile_class = {
> + .class_name = "subfile",
> + .item_name = av_default_item_name,
> + .option = subfile_options,
> + .version = LIBAVUTIL_VERSION_INT,
> +};
> +
> +static int slave_seek(URLContext *h)
> +{
> + SubfileContext *c = h->priv_data;
> + int64_t ret;
> +
> + if ((ret = ffurl_seek(c->h, c->pos, SEEK_SET)) != c->pos) {
> + if (ret >= 0)
> + ret = AVERROR_BUG;
> + av_log(h, AV_LOG_ERROR, "Impossible to seek in file: %s\n",
> + av_err2str(ret));
> + return ret;
> + }
> + return 0;
> +}
> +
> +static int subfile_open(URLContext *h, const char *filename, int flags,
> + AVDictionary **options)
> +{
> + SubfileContext *c = h->priv_data;
> + int ret;
Probably handled in other place, but you can check if flag doesn't
require writing.
> + if (c->end <= c->start) {
> + av_log(h, AV_LOG_ERROR, "end before start\n");
> + return AVERROR(EINVAL);
> + }
> + av_strstart(filename, "subfile:", &filename);
> + ret = ffurl_open(&c->h, filename, flags, &h->interrupt_callback, options);
> + if (ret < 0)
> + return ret;
> + c->pos = c->start;
> + if ((ret = slave_seek(h)) < 0) {
> + ffurl_close(c->h);
> + return ret;
> + }
> + return 0;
> +}
> +
> +static int subfile_close(URLContext *h)
> +{
> + SubfileContext *c = h->priv_data;
> + return ffurl_close(c->h);
> +}
> +
> +static int subfile_read(URLContext *h, unsigned char *buf, int size)
> +{
> + SubfileContext *c = h->priv_data;
> + int64_t rest = c->end - c->pos;
> + int ret;
> +
> + if (rest < 0)
> + return AVERROR_EOF;
If I remember correctly 0 should be returned. condition can be rest <= 0
> + size = FFMIN(size, rest);
> + ret = ffurl_read(c->h, buf, size);
> + if (ret >= 0)
> + c->pos += ret;
> + return ret;
> +}
> +
> +static int64_t subfile_seek(URLContext *h, int64_t pos, int whence)
> +{
> + SubfileContext *c = h->priv_data;
> + int ret;
> +
> + if (whence == AVSEEK_SIZE)
> + return c->end - c->start;
> + switch (whence) {
> + case SEEK_SET:
> + c->pos = c->start + pos;
> + break;
> + case SEEK_CUR:
> + c->pos += pos;
> + break;
> + case SEEK_END:
> + c->pos = c->end + c->pos;
> + break;
> + default:
> + return AVERROR(EINVAL);
> + }
seems like seeking below start offset will corrupt it.
For example SEEK_SET with pos equals to -c->start
--
Best Regards,
Lukasz Marek
I may be drunk, Miss, but in the morning I will be sober and you will
still be ugly. - Winston Churchill
More information about the ffmpeg-devel
mailing list